The oligomerization of olefins is known in the art, such oligomerization processes being effected by treating olefinic hydrocarbons with certain catalysts to obtain various oligomers which will find a useful function in the chemical art. One type of catalyst which may be employed for this particular type of reaction comprises a supported metal compound. For example, U.S. Pat. No. 3,562,351 discloses a method for dimerizing olefins utilizing a supported catalyst which has been prepared by impregnating a suitable support with a salt solution of a Group VIII metal followed by a heat treatment in an inert atmosphere at a temperature less than that which is required to form a metal oxide but which will form a complex on the surface of the solid support. Following this, the catalyst is activated by treatment with an organometallic compound. U.S. Pat. No. 3,483,269 describes a catalyst useful for oligomerizing lower olefins which comprises a .pi. -allyl nickel halide supported on an acidic inorganic oxide support. If so desired, the support may have been optionally treated with an alkyl aluminum compound. U.S. Pat. No. 3,592,869 also describes a catalyst which is useful for the oligomerization of olefins. A divalent nickel compound and an alkyl aluminum compound are contacted with an olefinic compound. The resulting mixture is then used to impregnate an inorganic refractory oxide support. Another patent, namely U.S. Pat. No. 3,644,564, describes a catalyst for the oligomerization of ethylene which comprises an organo aluminum-free reaction product of a nickel compound which is an atom of nickel in complex with an olefinically unsaturated compound and a fluorine-containing ligand. The catalysts are typically formed in situ. U.S. Pat. No. 3,679,772 describes a process for reacting monoolefins with diolefins, the catalyst for such a reaction comprising a complex of (1) nickel, (2) a group VA electron donor ligand such as an organophosphine, (3) a nonprotonic Lewis acid and (4) a reducing agent which itself may be a Lewis acid, all of which are composited on an acidic silica-based support.
U.S. Pat. No. 3,697,617 describes an oligomerization process involving the use of a catalyst comprising a complex of nickel with a chloro-containing electron donor ligand such as chlorodiphenylphosphine combined with a nonprotonic Lewis acid which is capable of forming a coordination bond with nickel and a reducing agent capable of reducing nickel acetylacetonate to an oxidation state less than 2. This complex may be composited on a solid support comprising an acidic silica-based material such as silica-alumina. The Lewis acid and the reducing agent may comprise the same compound as, for example, ethyl aluminum sesquichloride. U.S. Pat. No. 3,663,451 describes a catalyst which is obtained by reacting a transition metal halide such as nickel halide with a carrier to give a carrier-metal bond. This product is then reacted with a ligand such as a phosphine or ketone and finally activated by treatment with an aluminum alkyl or chloro alkyl.
U.S. Pat. No. 3,755,490 describes the polymerization of an olefin utilizing a catalyst comprising nickel, a Group VA electron donor ligand, a Lewis acid, and a reducing agent on a solid acidic silica-based support. U.S. Pat. No. 3,954,668 is drawn to an oligomerization catalyst comprising a nickel compound, a chloro-containing electron donor ligand, or a phosphorous compound, a nonprotonic Lewis acid reducing agent which is capable of reducing nickel acetylacetonate to an oxidation state of less than 2 and which is also capable of forming a coordination bond with a nickel. U.S. Pat. No. 3,170,904 speaks to a catalyst which is useful for polymerization comprising a large surface area metal of Groups VIIA or VIII of the Periodic Table, boron trifluoride etherate, an organometallic compound of Groups I, II, III or IV or a halo derivative of an organometallic compound of Groups II, III or IV or a hydride of a metal of Groups I, II or III. The large surface area metal which comprises one component of this catalyst is in metallic form as, for example, Raney nickel. If so desired, the catalyst may be composited on a diatomaceous earth carrier. In like manner, U.S. Pat. No. 3,170,906 discloses a catalyst which comprises (A) a carrier-supported nickel or cobalt oxide which has been prepared by impregnating the carrier with the hydroxide, organic acid salt, inorganic acid salt, followed by oxidation in the presence of oxygen or a combination of nitrogen and oxygen; (B) a boron, titanium, zirconium, or vanadium halide; and (C) an alkyl metal or alkyl metal halide. In addition to these patents, British Patent No. 1,390,530 describes an oligomerization catalyst which has been prepared by thermally pretreating a metal oxide carrier material followed by reacting with a halogen-containing organo-aluminum compound and thereafter in a step-wise fashion, impregnating this product with a divalent nickel or cobalt complex at temperatures ranging from -50.degree. to 150.degree. C.
Several other patents which describe oligomerization or polymerization catalysts which are unsupported in nature or processes include Japanese Patent. No. 5024282 which is drawn to a catalyst contain-ing a Group VIII metal and tin chloride or zinc chloride as well as Japanese Patent. No. 4722206 which describes an unsupported catalyst prepared by mixing a nickel compound, an aluminum organic compound and a tin tetrahalide. U.S. Pat. No. 3,155,642 describes an unsupported catalyst prepared from an alkyl tin compound and aluminum chloride in addition to a nickel or cobalt compound for the polymerization of a dienic compound. U.S. Pat. No. 3,155,642 also describes an unsupported catalyst comprising a nickel carboxylate, a halide of a metal of Group IV or V and an organoaluminum compound containing at least one alkoxy radical, said catalyst being used for the polymerization of cis-1,4-polybutadiene. Likewise, U.S. Pat. No. 3,457,321 describes an unsupported catalyst prepared from a complex organic compound of a metal of Group VIII, a reducing agent and a tin tetraalkyl compound. Furthermore, U.S. Pat. Nos. 3,483,268 and 3,505,425 are also drawn to unsupported catalysts, the former showing a catalyst comprising nickel acetyl acetonate, an organonickel compound, and an activating agent of an aluminum alkyl alkoxide or aluminum trialkyl while the latter is drawn to a process for preparing this catalyst. British Patent. No. 1,123,474 likewise teaches a process for preparing linear dimers using a catalyst comprising a complex organic compound of a metal of a Group VIII and a tin tetraalkyl compound.
In addition to the patents previously discussed another U.S. Patent, namely No. 4,757,042, relates to a catalyst for the oligomerization of olefins. The catalyst which is discussed in this patent comprises a complex of nickel or palladium, certain fluoro-organo sulfur ligands and an organo-metallic reducing agent. The fluoro-organo sulfur compounds or ligands comprise either fluoro-organo thiol or fluoro-organo sulfides, these compounds containing from 1 to about 20 fluoro substituents on the organo portion of the ligand. The catalyst is prepared by contacting the fluoro-organo thiol or fluoro-organo sulfide complexing agent with nickel or palladium or a salt thereof in an organic medium. Following this, the fluorothiol nickel or fluorothiol palladium complex is then admixed with a reducing agent to form the desired catalyst.
As will hereinafter be shown in greater detail the oligomerization of olefins to provide products which possess a minimal branching of the resultant chain may be accomplished by treating the olefinic hydrocarbons in the presence of the catalyst of the present invention, said catalyst maintaining its activity and stability, along with an increased amount of linear products at the expense of di-or other polysubstituents on the chain, for a relatively lengthy period of time even in the presence of certain impurities or poisons in the feedstock.